Process of stabilizing soil and soil additive product

ABSTRACT

A soil additive comprising a vinyl acetate homopolymer emulsion which includes vinyl acetate, hydroxyethyl cellulose, a nonatonic ethoxylated surfactant, potassium persulfate, sodium bicarbonate and water; a polyvinyl alcohol mixture which includes water, hydrogen peroxide, glycerin and polyvinyl alcohol; and a water repellent emulsion which comprises paraffin wax, an ethoxylated surfactant, diglycol stearate, candelilla wax, stearic acid, water, zirconium acetate, and ethylene urea resin. A process of injecting the additive into the soil is disclosed.

United States Patent 11 1 Hewitt. June 3, 1975 [54] PROCESS OF STABILIZING SOIL AND SOIL 3,303,147 2/1967 Elden 260/29.6 WA ADDITIVE PRODUCT 3,505,264 4/1970 Thoese..... 260/29.6 WA 3,563,851 2/1971 Armour 260/29.6 WA [75] Inventor: Robert L. Hewitt, Atlanta, Ga.

[73] Assignee: Terra Perma, Inc., Atlanta, Ga. rimary Xa in6 -]0 ePh L- SChOfel' Assistant ExaminerP. R. Michl [22] Ffled: 1973 Attorney, Agent, or Firm-Newton, Hopkins & [21] Appl. No.: 405,484 Ormsby 52 US. Cl... 260/17 A; 260/28.5 R; 260/29.6 NR; 1 ABSTRACT 260/29.6 404/75 A soil additive comprising a vinyl acetate homopoly- Int. Cl. mer emulsion includes vinyl acetate hydroxy- Field of search-m 17 ethyl cellulose, a non-atomic ethoxylated surfactant, 9-6 NR potassium persulfate, sodium bicarbonate and water; a

polyvinyl alcohol mixture which includes water, hy- References Cited drogen peroxide, glycerin and polyvinyl alcohol; and a UNITED STATES PATENTS water repellent emulsion which comprises paraffin 2809945 10/1957 wright 260/17 A wax, an ethoxylated surfactant, diglycol stearate, can- 2,350,46g 9/1958 Giggey 260/29 6 WA delilla wax, stearic acid, water, zirconium acetate, and 3,003,979 10/1961 Ptasienski 260/29.6 WA ethylene urea resin. A process of injecting the additive 3,094,500 6/1963 Herman 260/29.6 WA into the soil is disclosed. 3,197,429 7/1965 Baatz 260/29.6 WA 3 213 51 10 19 5 1 Claim, N0 Drawings Pink 260/29.6 WA

PROCESS OF STABILIZING SOIL AND SOIL ADDITIVE PRODUCT BACKGROUND OF THE INVENTION The present invention relates to a soil additive which alters the soils density and water permeability.

Heretofore, soil stabilization methods using cement had certain drawbacks: for example, the cement particles were subjected to a filtration action in the ground, therefore giving inferior permeability into the minute interstices of the soil. This, of course, restricted the scope in which a product of this type could be used.

Later, chemical soil stabilizing processes were developed using monomers, solutions of urea, formaldahyde resins and other additives; however, these types of systems required polymerization in the soil by the addition of curing agents. These products and methods have not been satisfactory because the chemicals injected into the soil are not uniform and therefore the results were not reproducible.

There are a number of prior art patents in which are found various fomulations for different types of agents which may be added to the soil. The patent to Hedrick et al., U.S. Pat. No. 2,652,379, discloses a soil additive which loosens tightly compacted soils and comprises a partially hydrolyzed polyvinyl ester such as polyvinyl acetate polyvinyl alcohol. The polymer may be applied to the soil in the presence of a solvent or extender such as water or a solid carrier such as peat moss, limestone, sand, clay, mineral fertilizer, silage or some other fertilizer.

French Pat. No 1,232,237, issued to Karata, discloses a soil additive which is an emulsion of polyvinyl acetate as the principal component of a polyvinyl acetate polymer which contains polyvinyl alcohol which is derived by the partial saponification of polyvinyl acetate.

The patent of Routson, U.S. Pat. No. 3,520,141, discloses a composition useful in rendering soils less permeable to the passage of water and which consists of polyvalent metal ions and certain polymers which include anionic and nonionic water-soluble polymers. Water dispersible latex polymers include homo and copolymers of vinyl acetate, methyl or ethyl methacrylate, and the like.

The patent to Deming, U.S. Pat. No. 3,016,713, shows a composition which prevents infiltration of porous 'soil surfaces by water from conduits or reservoirs and which consists of a lattice clay such as bentonite, montmorillonite, hectorite, saponite or the like and an anionic polyelectrolyte such as a coploymer of an unsaturated carboxylic acid and vinyl acetate, vinyl formate, vinyl alkyl ether or the like.

The Sakata et at., patent, U.S. Pat. No. 3,495,412, discloses a process for forming a gel-like material in a soil by injecting into the soil an aqueous solution comprising urea, formaldehyde and poylvinyl alcohol and thereafter curing the solution with an acidic solution. The additive renders the soil water impermeable.

BRIEF SUMMARY OF THE INVENTION The present invention is a stabilizing agent which is mixed with native soil in proportions and to a depth indicated by laboratory tests. Classification and Proctor tests are made to determine the grain, organic content and percentage of natural mositure present in the soil. These tests confirm the amount of the product to be added, check the cure cycle time, optimum soil content and precise mix measurements. Compaction requirements are also lab tested.

The additive includes a polymer, a water repellent, cross-linking agents and plasticizers and more specifically, comprises:

1. 80 90% by volume of a vinyl acetate homopolymer emulsion composed of vinyl acetate, hydroxyethyl cellulose, a non-ionic ethoxylated surfactant, potassium persulfate, sodium bicarbonate and water;

2. 5 10% by volume of'a polyvinyl alcohol mix composed of polyvinyl alcohol, hydrogen peroxide, glycerine and water; and

3. 5 10% by volume of a water repellent emulsion composed of paraffin wax, an ethoxylated surfactant, diglycol stearate, candelilla wax, stearic acid, zirconium acetate, ethylene urea resin and water.

All three ingredients are combined in measured amounts and mixed thoroughly together before injection into a given soil. Creation of the stabilized, treated soil (the soil particles having been bound together by the additive) is obtained by natural air curing process. The elimination of additional curing agents once the premeasured amount of additive has been injected into the soil, eliminates the possibility of errors and more uniform curing can be obtained.

DETAILED DESCRIPTION OF THE INVENTION The following is an example of the composition of the soil additive:

1. Vinyl Acetate Homopolymer Emulsion By Weight Vinyl Acetate 55.00 Water 42.75 Hydroxyethyl cellulose 2.00 Non-ionic ethoxylated surfactant 0.05 Potassium persulfate 0.05 Sodium Bicarbonate 0.15

Procedure 1. Charge the hydroxyethyl cellulose, surfactant and water in a reaction flask and heat by means of a water bath at 80C. Maintain heat one hour and cool to 30C.

2. Add the potassium persulfate, sodium bicarbonate and 10% by weight of the total vinyl acetate monomer.

3. Heat the reaction mixture to C. C. (vinyl acetate water azeotropes at 66C. 68C.). At this temperature, start a delayed addition of the remaining 90% vinyl acetate monomer through a graduated dropping funnel. Add at a uniform rate, maintaining an 2C. temperature, throughout a 3 4 hour addition period.

4. At the end of the monomer addition, hold for 15 30 minutes and then heat the reaction to C. 92C. Retain at this temperature. Filter the finished emulsion through cheesecloth.

Average Physical Properties Brookfield Viscosity 3320 cps No. 3 spindle, 30 rpm Percent solids (observed) 54.3 Ph 5.0

2. Polyvinyl Alcohol Mix -Continued by Weight Water 63.0 Hydrogen Peroxide 2.0 Glycerine 2.0

3. Water Repellent Emulsion In an alloy kettle, melt at 85C. 90C.

by Weight Paraffin wax 17.00 lO-mole ethoxylated surfactant 2.30 Diglycol stearate 1.00 Candelilla wax 5.10 Stearic acid 2.55

After the above mix has completely melted, add slowly pre-heated water at 80C. 85C.

Water (Gallons) After all the water is added and a uniform mix is obtained, add:

Zirconium acetate (22% solution) 5.95 Cut off the heat. Do not whip in air, but allow to cool while stirring at 45C. 50C. add:

Ethylene urea resin 15.00

Cool and draw the emulsion.

As the final step, 80 90% by volume of the vinyl acetate homopolymer emulsion, 5 by volume of the polyvinyl alcohol mix and 5 10% by volume of the water repellent emulsion are mixed together in a Ribbon Blender until a uniform blend is obtained. The final product can then be packaged in lined drums or stainless steel tanks to prevent rusting.

The finished product has a balanced composition to give the best performance with varied grain size, soil and aggregate compositions for optimum resistance to water of the treated material. It may be used in the construction of roadways, parking lots, aircraft runways, heliports, outdoor storage plarforms, tennis courts, athletic tracks and other surfaces requiring stabilization and solidification. It has demonstrated that it will solidify most classifications of soils as listed by the US. National Cooperative Soil Survey and is also used as a complete substitute for hot asphalt aggregate. The latter operation may be done in an on-site mixer or at a base pugmill plant.

The required stabilization and resistance to total pound loads and water is obtained by varied percentages of the product injected into the soil or aggregate determined by prior specifications designated in laboratory tests conducted on the soil or aggregate samples obtained from actual sites. To determine how much of the soil additive can be added to the soil, the moisturedensity relations of the soil-should be determined by the Soil Proctor Test, according to ASTM D 698-70. In this manner, the optimum moisture content of the soil per volume of soil can be determined, thereby allowing calculation of the amount of soil additive and water which can be injected into the soil.

In conducting laboratory strength value test on the soil specimens, test procedure ASTN D 1559-71 is followed. First, a mixture of the soil, water and the additive is made in a mixing bowl. Next, compaction of the specimen is accomplished by cleaning the specimen mold (4 inch diameter) and the face of the hammer 10 lbs, sliding weight with a free fall of 18 inches). Place the entire batch in the mold and spade the mixture vigorously with a trowel 15 times around the perimeter and 10 times over the interior. Remove the collar and smooth the surface of the mix with a trowel to a slightly rounded shape. Replace the collar. Place the mold on the compaction pedestal in the mold holder, and apply 50 blows with the compaction hammer. Remove the base plate and collar and reverse and reassemble the mold. Apply the same number of blows to the face of the reversed specimen. Carefully extrude the specimen out of the mold, and allow it to stand overnight at room temperature.

Approximately after six days of air curing, unless otherwise specified, immerse the specimen in water and allow it to soak four hours. Then remove the specimen from the water bath, place the specimen between both segments of the breaking head, and place the complete assembly in position on the Marshall testing apparatus. Apply the load to the specimen by means of the constant rate (2 inch 50.8 mm/min.) until the maximum is reached as indicated by the dial gauge. Then calculate maximum load in lbs. or kg. and include correction when required.

EXAMPLE 1 A sample of soil was obtained from a roadbed in the Newton County, Georgia area. The gredation of sample was passing through a No. 4 sieve, having a maximum dry density of 110.1 pcf (1764. kg/m), a natural moisture content of 17.6% and an optimum moisture content of 16.8%. The soil was classified as red-brown, slightly micaceous, silty fine to coarse, very sandy clay with some inch rock fragments.

Material content and strength values for various additive proportions by using soil material compacted at g. of Standard Proctor No. 2 are as follows in Table l.

The additive was then utilized to convert the road into a dust-free hand surfaced street. The above tests indicated the porportions and depth into the native soil the additive had to be mixed. A Galion motor grader scarified the roadbed to a depth of 6 inches. Next, a Rex Stabilizer reduced the soil to a fine, uniform consistency.

A water truck loaded with the additive and water, mixed nine to one as indicated by the lab tests, wetted the prepared soil at a present flow rate. The stabilizer then made another pass to thoroughly mix the soil and the applied waterstabilizer mixture. The roadbed was then completed by compacting with a vibratory roller.

Test cores were taken of the treated roadbed periodically for 15 days to verify solidification. These tests indicated strengths ranging from 310 to 570 psi, with 520 psi average. Normal traffic use was possible five to eight days after installation.

EXAMPLE 11 Stability tests were run on specimens of aggregate mix and the present invention, the aggregate having the following mix composite:

Coarse aggregate Stone, No. C Stone, No. 7

vibrate in order to reduce cracking. Heavy equipment should be restricted from surface until a reasonable amount of cure has set in. Problem areas should be hand racked or portable mixed into soil that occur after Fine Aggregate 5 installation. It also is recommended that core testing Manufactured sand, No. 4 and No. 200 400 grains. under standard procedures (ASTM) should be done to 72 cc (6% of the dry weight of the mix composite) of check specification and prior laboratory results.

thesoil additive was mixed into the aggregate. Six Mar- An ideal distribution of particle size in a road mateshall patties, each patty having 1,200 grains, dry weight rial from coarse aggregate down to fine binding soil of the total mix, were molded, soaked in water for l5 would be as follows: hours and then tested. (See Table I1) Passing EXAMPLE III 1 inch sieve 100 An asphalt binder aggregate was prepared, having a 1 5 i Sieve 70 100 inch sieve 58 8O coarse aggregate of Stone No. 57 (300 grams) and 4 Sieve 35 65 Stone No. 7 (300 grains) and a fine aggregate having No. 10 sieve 25 50 a sieve site No. 4 No. 200 (600 grains). 73 cc (6% of 388223 2: 2 the dry weight of the mix) of the soil additive was added. The mix composite was molded into a Marshall The Sample Soil shown above will give the best patty' (see Table sults, but good roads can be obtained with a wide vari- A general method of mlectmg the present mvennon ety of soil types and particle size distributions. Since mm a roadbed as follows: soils are usually complex mixtures, a soil test engineer Grade the road to get of corrugathms and pot can help find the right treatment for the particular soil. holes to loosen the road Surface matenal to depth This may involve the addition of clay to sand to gravelly Patten-anon Remove large rocks t would Cause soils, and the addition of sand and gravel to clay soils equPment l l or b e h g Smgle or to get the best and most economical results. The closer mum bl j S rapld dramage Important the road materials approach the ideal, the less of the to the S01] addltwe 1t ls recommended that an A type present invention required and the longer the treated crown modified cross section with a uniform center line road Surface will last In most cases, the cost f the and side slopes of One-half inch p r foot from the plied additive will determine whether or not you should ter line to the edge of the road be utilized. A moisture dif the Soil composition I extreme cases, h test must be made on site at time of installation to deever, the Soil composition must be difi d to even termthe the dilution factor of the Product make the road serviceable, regardless of whether the The best method of installation is to use a multi or additive is used or not single stabilizer Processed y a water tank with the If there isahigh water content in the soil, another inmixed soil additive feed back to the Ptllverizer under gredient which can be added to the additive, is sodium Pressure and regulated to the gallons P minute to the silicate which acts as a catalyst to absorb water and dry square yard or meter to bring the sell to Optimum, as the product in the soil. Too much sodium silicate will per the design specifications. If preferred, the diluted 40 result in cracking Usually 2 5% by weight of the additive can be installed in one-half or one-third di ili can b dd d t th il dditi amounts under a multi pass bases in layers rather than Addi i ll a d can b i d with th additive to apply the total amount at one time aid in application identification.

Soil should he allowed to y back as necessary to The present invention has a comparable cost to soil allow compaction equipment to gain access to the stacement for installation and an additional savings in bilized soil. it is not necessary to blade off stabilized soil i d b F h test d f E l I h i. into windrows or berms. Final compaction can best be ated cost was 60 cents per square yard. A single pass obtained with wheeled rubber tire roller or a vibratory bili i r would have reduced the labor costs compactor. Care as always should be used not to over even more TABLE 1 STRENGTH WET OF SOlL DENSITY MOISTURE DRY TEST AT STRENGTH ADDlTlVE (Kg) WATER ADDlTlVE (Kg/m) CONTENT DENSlTY (days) PS1 3% 6 lbs. 279.8cc 8.7cc 119.4 pcf 9.1% 109.4 pcf 15 (2.7) (1912.5) (1752.5) 6% 6 lbs. 271.2cc 17.3cc 120.0 pcf 9.4% 109.7 pcf 15 690 (48.5)

(2.7) (1922.2) (1757.2) 971 6 lbs. 262.5cc 260cc 119.7 pcf 9.1% 109.7 pcf 15 840 (59.1)

(2.7) (1917.4) (1757.2) 12% 6 lbs. 253.900 34.600 118.8 pcf 8.491 109.6 pcf 15 970 (68.2)

( Values Expressed by the Metric System.

TABLE II HEIGHT SPE- UNIT WEIGHT STABILITY, TOTAL CIFIC LOAD NO. IN. CM. GRAV PCF Kg/m LBS. Kg.

ITY

TABLE III HEIGHT SPECIFIC UNIT WEIGHT STABILITY, TOTAL LOAD NO. IN. CM GRAVITY PCF Kg/m LBS. (Kg) 1. 2.5 (6.4) 2.189 136.6 (2188) 11.200 (dry) (5080) 2. 2.5 (6.4) 2.240 139.8 (2239) 6,200 (2812) Note: Sample No. 2 was soaked in water for 72 hours. Compression tests for both specimens were performed by using Marshall apparatus. 1 Values expressed by the Metric System.

comprising water, hydrogen peroxide, glycerin and polyvinyl alcohol; and from 5 10% by weight of a water repellent emulsion comprising wax, an ethoxylated surfactant, diglycol stearate, stearic acid, zirconium acetate, ethylene urea resin and water. 

1. AN ADDITIVE FOR STABILIZING IN SITU WATER PERMEABLE SOIL COMPRISING FROM 80 - 90% BY WEIGHT OF A COMPOSITION COMPRISING VINYL ACETATE HOMOPOLYMER, HYDROXETHYL CELLYLOSE, A NON-IONIC ETHOXLATED SURFACTANT, POTASSIUM PERSULFATE, SODIUM BICARBONATE AND WATER; FROM 5 - 10% BY WEIGHT OF A POLYVINYL ALCOHOL MIXTURE COMPRISING WATER, HYDROGEN PEROXIDE, GLYCERIN AND POLYVINYL ALCOHOL, AND FROM 5 - 10% BY WEIGHT OF A WATER REPELLANT EMULSION COMPRISING WAX, AN ETHOXYLATED SURFACTANT, DIGLYCOL STERATE, STERIC ACID, ZIRCONIUM ACERATE, ETHYLENE UREA RESIN AND WATER. 